Ocular emergencies--what to do next

Ophthalmic emergencies require immediate professional attention to maintain vision, health of the globe and relief of ocular pain. Any animal exhibiting acute ocular pain, deformity of the globe or orbit, acute loss of vision or a sudden change in appearance of the eye should be treated as an emergency. The maintenance of pulmonary, cardiovascular, hemodynamic and neurologic functions take precedence over vision in emergency situations.

Remembering the posterior segment…Treat all "acute" losses of vision as a potential emergency. Pain and externally visible inflammation may not be accompanied with blindness. Quick intervention is more likely to restore sight, preserving the function of the retina and optic nerve. Vision loss can require time sensitive intervention and if a diagnosis can't be determined quickly, consultation with an ophthalmologist is advised.

Orbital examination

The orbit cannot be directly examined, and therefore, a variety of evaluation techniques and diagnostics are used. A visual inspection of the globes will allow you to estimate the degree of exophthalmos or enophthalmos relative to the contralateral eye. Observation of the displacement can also help to localize the lesion, as shown in the picture (Slatters 4th Ed, pg 357). On oral examination, ability to open the mouth is suggestive of the type of disease. Inability to open the mouth is suggestive of restrictive myopathy.  Pain associated with opening the mouth suggests inflammation, where lack of pain suggests neoplasia. Swelling behind the last molar on the ipsilateral side is also indicative of orbital disease.

Retropulsion of a globe with a normal orbit can be quite substantial in dolicho- and mesaticephalic dogs, but can be less so in brachycephalics. An orbital lesion will restrict retropulsion of the globe. Palpation should also be performed caudal to the orbital ligament and around the orbital rim.

Orbital fractures

In dogs this is most commonly associated with MVA. Don't forget to evaluate the neurological status and for entrapment of the globe by retrobulbar bone fragments. Physical examination tends to be of greater value than radiographs. Symptoms may include pain, swelling, crepitus (acute), exophthalmos or enophthalmos, strabismus, retrobulbar or periocular hemorrhage, facial asymmetry, deviation of the globe, proptosis, orbital emphysema (sinus involvement) or epistaxis (sinus involvement). Always palpate along the orbital rim for symmetry. Step defects are usually easy to palpate. If an orbital fracture is likely, then a CT is recommended. Frontal, temporal, and zygomatic bones are most commonly involved in the dog. (Supraorbital process and lacrimal bone fractures common in the horse.) Cats typically have multiple fractures of the head.

Orbital imaging

Imaging is very important in evaluation of the orbit. Plain radiography may possibly be of little diagnostic value in the orbit. Contrast radiography has been frequently used over the years, but has been mostly replaced by newer imaging techniques including ultrasound, color Doppler imaging, CT, and MRI. Newer imaging techniques allow precise location of lesions, and facilitate a precise treatment plan.

Orbital abscess/cellulitis

Patients will often exhibit pain on opening mouth. Examination, for an orbital foreign body is important and may require anesthesia. Treat with systemic antibiotics and oral antiinflammatories. Although written in many textbooks, surgical drainage behind the last molar does not always yield copious egress of exudate. I would only establish drainage if that approach was supported by imaging. Topical lubricants can be used to address exposure keratitis.

Inflammatory diseases of the orbit are more common in small animals compared to large animals. Orbital inflammation can be sterile or infectious in nature. Infectious causes are most frequently bacterial, which can invade the orbit by a number of different routes. There are many reports of orbital foreign bodies including pieces of wood and plant material, as well as porcupine quills and metal. Bacteria can also invade from neighboring tooth roots or sinuses, or can spread hematogenously to the orbit.

Please consider the following reference. Wang AL et al. Orbital abscess bacterial isolates and in vitro antimicrobial susceptibility patterns in dogs and cats. VO. 2009; 91-96. This study evaluated dogs and cats diagnosed with orbital abscess based on aerobic and anaerobic culture results, and confirmed by response to therapy, orbital imaging, and cytological or histopathological examination. Cultures were collected transorally, transconjunctivally, transcutaneously, or at necropsy.

Etiologies were highly variable. In dogs, etiologies included idiopathic, extension from adjacent structures including tooth roots, pharynx, and tympanic bullae, penetrating traumas, foreign bodies, post-operative infections, orbital penetration during dental prophylaxis, and blunt trauma. In cats, the etiologies included idiopathic, stomatitis, Cuterebra migration, and orbital penetration during dental prophylaxis. 100% canine isolates were susceptible to ceftiofur and ticaricillin, and greater than 90% were susceptible to TMS, amikacin, gentamicin, and imipenem. Organisms from feline isolates were susceptible to everything except clindamycin and erythromycin.

Penetrating ocular foreign bodies - Gunshot and plants most common. Therapy is dictated by composition of the foreign material, its position, and the degree of inflammation. Plant material has a high rate of infection (bacterial or fungal). Any of the following may be noted: acute exophthalmos, periorbital swelling, pain on palpation and opening of mouth, TEL elevation, chemosis, mucopurulent ocular discharge, fistulous tracts, retinal detachment, pyrexia, and leukocytosis.

Gunshot pellets may be best left alone as these rarely get infected. Explore gunshot wounds only if globe integrity is in question, there is heavy wound contamination or persistent bleeding. Patients usually present with hyphema and pain. Radiographs with a metal ring outlining the limbus may help determine the pellet's position and extent of ocular injury.

Proptosis

Proptosis is often secondary to HBC or bite wounds. More common in breeds with prominent eyes, shallow orbits and wide palpebral fissures as these breeds require less trauma to produce proptosis. A much greater force (and hence a poorer prognosis) is required to proptose the globe in breeds with a deeper orbit. For cats, or species with complete bony orbits (i.e., cattle, horses) the force is tremendous and prognosis very poor. Once the globe is displaced forward, the lids contract behind it, mechanically constricting venous return. Adnexal swelling and hemorrhage due to the primary injury, prevents the eye from returning to the orbit. Favorable prognostic indicators include: brachycephalic dog, positive direct or consensual pupillary light response, normal findings on posterior segment exam. Unfavorable indicators include: non-brachycephalic breed of dog, any cat breed, avulsion of 3 or more extraocular muscles, hyphema, no visible pupil, and facial fractures.

Treat by repositing globe under anesthesia. Lubricate the corneal surface and perform a lateral canthotomy if needed. Pre-place sutures (simple interrupted; horizontal mattress, 5-0 non-absorbable suture. Apply stents (ex. fluid line tubing). Simply apply gentle traction by pulling the lids over the globe.

Please consider reviewing the following reference: JAVMA ‘95. Gilger. Traumatic ocular proptoses in dogs and cats: 84 cases. In summary, 45/ 66 dogs and 2/ 18 cats had replacement of the eye and temporary tarsorrhapy. 26/ 45 (58%) of eyes were blind on re-evaluation. Only 27% of dogs were considered visual. All cats were considered blind. 3/ 45 eyes were enucleated after reevaluation due to severe corneal disease. Brachycephalic dogs had a better chance at a visual outcome.

Acute anterior lens luxation

Primary lens luxation is a bilateral inherited condition seen mainly in the terrier breeds that results in gradual zonular breakdown and subsequent dislocation of the lens. The average age of onset is 4.5 yrs. A hereditary basis has not been reported in the cat. Lens dislocation in the cat occurs most commonly as a secondary sequela to anterior uveitis, glaucoma, or trauma. Secondary lens dislocation is commonly seen with hypermature cataracts, glaucoma, and uveitis. Trauma may initiate lens movement in those breeds with a hereditary predisposition. However, the amount of blunt force needed to dislocate the lens from its zonular attachments in a non-predisposed eye would result in severe ocular injury.

Breeds are Jack Russell Terrier**** and any other terrier!, Chihuahua, Shar Pei, Chinese crested, Cattle dogs, German Shepherd. Patients present with acute blepharospasm, acute red eye, acute corneal edema. These patients will often have secondary glaucoma, but do not respond well to anti-glaucoma medications due to the mechanical obstruction from lens entrapment in the anterior chamber. Other complications are are corneal endothelial cell degeneration (often described as a kissing lesion), and retinal detachment secondary to excessive movement of vitreous base.

These types of retinal detachments often necessitate retinal reattachment surgery. Pre-op electroretinography is important as the retina may have already been irreversibly damaged because of glaucoma. Long-standing anterior lens luxations tend to be permanently blind. Surgery for immediate lens remove to restore vision, prevent uveitis, glaucoma, corneal damage, and retinal disease is an emergency. You can treat associated glaucoma with mannitol IV, topical steroids if no ulcer, as well as systemic anti-inflammatories and analgesics. It is important to closely inspect the fellow eye as it is often sub-luxated in those breeds with an inherited predisposition. Topical application of a miotic to the fellow eye will allow the iris to buttress the lens in the posterior segment of the eye and decrease the likelihood of anterior luxation leading to blindness.

Please consider the following reference. Binder et al. Outcomes of nonsurgical management and efficacy of demecarium bromide treatment for primary lens instability in dogs: 34 cases (1990-2004). JAVMA 231 (1) 2007. Demecarium Bromide or Xalatan can decrease the time to luxation in the fellow eye, but it still can occur especially considering all factors: activity of the dog, drug resistance and client compliance.

Optic neuritis

This is a true emergency presenting as sudden, often bilateral blindness but the condition can be unilateral. Pupils are generally fixed and dilated. A normal ERG differentiates it from SARDS. There are numerous etiologies. The optic nerve head may look normal or abnormal. Retrobulbar optic neuritis will present with normal appearing optic nerve heads and make the diagnosis difficult without imaging. When the optic papilla is affected it will appear swollen and edematous with fuzzy disc margins. The physiologic cup may be indistinguishable as well. Peripapillary hemorrhages are commonly seen. Adjacent retinal vascular tortuosity may be observed and sometimes and peripapillary retinal detachment or retinal edema. I consider optic neuritis cases to generally fall in to immune-mediated, infectious, inflammatory, or granulomatous.

Causes of optic neuritis in small animals are distemper, tick-borne diseases, blastomycosis, cryptococcosis, histoplasmosis, coccidioides, aspergillosis or other fungi. Optic neuritis may result from inflammatory conditions that are anatomically contiguous such as the paranasal sinuses, retina, brain, mininges and orbit. Therefore orbital abscess/cellulitis, and orbital neoplasia can cause optic neuritis. In order to initiate therapy, labwork, chest radiographs with CSF tap and MRI are recommended.

Immune-mediated optic neuritis-this is the most common form seen by veterinary ophthalmologists. I generally administer IV steroids followed by several months of steroids or as needed as the condition may often need to be controlled due to recurrence. I believe systemic steroid therapy is recommended early to restore sight even in the face of an infectious disease. Studies have also show better efficacy of antibiotics or antifungals following the quick reduction of inflammation with steroids.

Retinal detachment

A retinal detachment occurs with the neuroretina separates from the underlying RPE. This region is intimate and essential but structurally weak! Small areas of retinal detachment will not cause dogs to show noticeable vision loss but when greater areas of detachment occur, vision will deteriorate and possibly ultimately lead to complete blindness. The peripheral retina is thinner and more likely to tear. Tears in the retina are addressed surgically. Fluid will collect beneath the retina and often result in the appearance of bullous detachments. The height of the detachment can be so extreme that it touches the posterior lens. Lower height detachments are less obvious.

Retinal detachments are characterized as rhegmatogenous (having a tear), exudative, or tractional. Rhegmatogenous detachments are the most common in the dog. They can present as a primary problem in particular breeds (such as the Shih Tzu, Poodle, Maltese, etc.) and tears can also occur secondary to cataract surgery. Tractional components often play a role post cataract surgery as well. Exudative detachments occur by infectious and inflammatory processes. Infectious etiologies include bacterial, fungal, and rickettsial. Hypertension can also lead to detachments and is often seen in cats. Exudative detachments with no cause is not uncommon, and termed steroid-response retinal detachments. Dogs typically have acute onset of vision loss and they have NON-rhegmatogenous detachments. I have seen a tremendous number of these in German Shepherds and Australian Shepherds.

Photoreceptors begin to degenerate in 1-3 days so a quick diagnosis, and treatment based on cause provides the best outcome for the patient. Depending on the cause even extensive detachments may have near complete restoration of vision.